Signaling system



' Nov. 21, 1939.

H. A. BREDEHOFT SIGNALING SYSTEM Filed Jan. 20, 1938 2 Sheets-Sheet I IN [/5 N TOR By H. A. BREDEHOF r ATTORNEY Nov. 21, 1939. BREDEHOFT 2,180,334

SIGNALING SYSTEM Filed Jan. 20, 1938 2 Sheets-Sheet 2 8 HABREDEHOFT' ATTORNEY Patented Nov. 21, 1939 TATS ATEN'l SIGNALING SYSTEM Application January 20, 1938, Serial No. 185,852

14 Claims.

This invention relates to signaling system and particularly to systems for operating signals at intervals.

An object is to provide signaling arrangements of this type which are simple in construction and reliable in operation.

Heretoiore signals have been operated at intervals by the aid of glow tubes and other discharge devices. Such systems have also been employed in telephone systems for operating ringers at substations at intervals by the application of alternating current at intervals at a central ofiice.

It is a feature of the present invention to provide a system for operating a subscribers ringer at a substation at intervals by the continuous application of ringing currents to the subscribers lines from a central ofiice.

Another feature is an arrangement in which the signal may be operated at intervals increasing in frequency until the signal is operated steadily by the application of current thereto. The circuit arrangement for this system includes two discharge tubes. The operation of a subscribers ringer at intervals necessitates the conversion of the ringing current from the central ofiice into direct current by one tube while the other tube, in series with a, condenser, is used for the operation of the ringer at intervals. The arrangement for operating the signal at intervals increasing in frequency includes, in addition to these two discharge tubes, an element such as boron having a non-linear resistance characteristic.

The invention has been illustrated in the accompanying drawings in which: 7

Fig. 1 shows a circuit arrangement in accordance with the applicants invention for operating a ringer at a substation at intervals by the continuous application of alternating currents at a central office;

Figs. 2 and 3 show modified forms of the applicants invention as disclosed in Fig. i;

Fig. 4 shows a circuit arrangement in accordance with the applicants invention for operating a signal at intervals increasing in frequency by the application of alternating current; and

Figs. 5 and 6 show modifications of the applicants invention as disclosed in Fig. 4 applied to a telephone system.

Referring now to the drawings and particularly to Fig. l, a key I has been shown at a central of ice G which may be operated to apply current from the alternating current source 2, which may be the usual ringing current source, to the two conductors of a telephone line 3 ter- (Cl. Nil-84) minating at a substation SA in a telephone set T and a ringer joined to the line 3 through tubes 6 and I connected in a circuit in accordance with the applicants invention. These tubes may be of any well-known type including a cathode, an auxiliary control electrode and a main anode. These tubes operate by the usual method of establishing a potential between a control electrode and a cathode to cause ionization of the tubes to start a discharge between the main anode and the cathode as is well known in the art.

The system as disclosed in Fig. 1 operates as follows: When the key I is operated, alternating current from the source 2 is applied to the conductors of line 3. This establishes a potential difference between the cathode 8 and the control electrode 9 to cause ionization in a tube 6. This in turn causes rectified current during the positive half wave to flow over a circuit from source 2, key I, resistance 5, condenser H, anode ll cathode 8, key 1 to ground. As the ionization of the tube is continuous, this current is maintained and may comprise a series of positive impulses more or less atenuated to form a continuous undulating direct current. This direct current now begins to charge condenser ll. As the opposite terminals of this condenser are connected respectively to the control electrode l2 and the cathode is of the tube l, a corresponding potential difierence will be established between these electrodes. Depending now on the characteristics of the tube, this potential will cause ionization in tube l when the charge on the condenser has reached a certain value. When this takes place current will flow through the tube over a circuit from key l, resistance d, windings of ringer 5, anode Hi and cathode is of tube 1, anode l6 and cathode 8 of tube 6, key l to ground. The condenser it now discharges through the tube '1 between the control electrode l2 and the cathode l3 and this decreasesthe potential difference between these electrodes to a point where ionization ceases which in turn interrupts the flow of current through the tube l and the ringer 5. It should be observed that the discharge of condenser it takes place at a comparatively rapid rate and the ringer 5 will, therefore, operate for a correspondingly short interval. The charging process of the condenser H from current through tube 6 is, however, continuous, but takes place at a comparatively slower rate. Hence, these operations of charging and discharging the condenser may take place at repeated intervals of time and at a rate to cause the ringer 5 to be repeatedly operated at intervals determined by the electrical characteristics of tubes 6 and I, condenser I i and resistance 4.

As is usual in systems of this type when the subscriber answers a call by lifting his receiver from the switchhook in his telephone set T, the usual tripping relay at the central office will operate to disconnect the alternating current source 2 from the line and connect the talking battery for conversation. The talking battery will, of course, be of such character as not to cause the tube 6 to operate.

Fig. 2 is practically identical with Fig. 1 except that the circuit for charging the condenser II extends between the control electrode 9 and the anode IE3 and a resistance I8 has been inserted in this circuit to delay or regulate the period of charging the condenser. The periods between the intervals of operation of the ringer 5 may therefore be increased or decreased as required by varying the resistance I8. The circuit for the ringer 5 has also been shown somewhat differently in that it does not extend through the tube 5, but is instead connected from the cathode I3 directly through key I to ground. A condenser I! may also be inserted in the ringer circuit to quicken the operation of the ringer on each impulse.

Fig. 3 is identical with Fig. 2 except that a howler arrangement I5 has been substituted for the ringer 5 to cause a tone to be produced at intervals.

Fig. 4 shows a circuit similar to that disclosed in the preceding figures arranged to operate a ringer at intervals increasing in frequency. To accomplish this a boron element Zii, or any other element having a negative coefiicient of resistance, has been inserted in the circuit for charging the condenser II between the anode I and the resistance I 8. This circuit operates as follows: When the tube 6 first operates, the period of charging the condenser Iii sufiiciently to cause tube I to operate will .depend on the initial resistance of the element 26, and, as this initial resistance is at its highest value at this time, the first charging period will therefore be of a certain corresponding duration. When the tube I ceases to operate the second period of Charging the condenser will occupy a comparatively shorter time interval as the resistance of the element 26, due to its change in temperature, has decreased. Tube '1 will, therefore, operate the second time at a shorter time interval after the recharging of the condenser I I than after the first charging of the condenser. It also follows that succeeding operations of the tube 7 will take place at correspondingly shorter intervals as determined by the continuous decrease of resistance of the element 20. That is to say, the longer the circuit is closed from the source 2, the shorter will be the succeeding charging periods of the condenser II and the operation of tube 1 will therefore take place at intervals increasing in frequency. Hence, the ringer may by means of this circuit arrangement be controlled to operate at intervals increasing in frequency and the rate of increase in frequency may be adjusted to suit any desired requirement. For example, the resistance I8 and the element 20 may be adjusted to cause the increase in frequency of the operation of the ringer 5 to be such that the ringer will eventually operate at a constant rapid rate giving the appearance of continuous ringing. A condenser 22 and a resistance 2 may be inserted in the circuit for the cathode 8 and control electrode 9 to insure quick initial operation of the tube 6 and reduce the current drain during the maintaining of this tube in operation. This circuit has not been shown applied in a telephone system as the features of the invention as illustrated in this figure may be applied to any system in which it is required that a signal be operated at intervals increasing in frequency.

Fig. 5 shows the principles of the system disclosed in Fig. 4 applied to a telephone system and the circuit for ringer 5 is similar to that shown in Fig. 4. It is, however, somewhat differently arranged in that the control electrode 9 is connected directly to ground while the source of current at the central oflice comprises an alternating current source 2 and a direct current source 25 in series connected in a circuit from the cathode 8, resistance 23, key I, alternating current source 2, direct current source 25 to ground. Hence the source of current in this circuit has a positive bias as the direct current from source 25 is superimposed on the current from the alternating current source 2. The ionization of the tube 6 will therefore be initiated by the voltage of cathode 8 and the ground potential on control electrode 9. Otherwise this circuit functions in the same manner as the circuit in Fig. 4.

Fig. 6 is similar to Fig. 5 and operates in the same manner except that the circuit for establishing the ionizing potential between the cathode 8 and the control electrode 9 extends from ground, the direct current source 5, the alternating current source 2, key I, condenser E I, resistance I8, element 20, resistance 25, cathode 8 and the ionization of tube 6 is caused by the voltage on cathode 8 and the ground potential on the control electrode 9.

What is claimed is:

1. In a telephone system, a central office, a subscribers station, a line connecting said central ofifice and station, a source of ringing current at said central oifice connectable to said line, a ringer at said station connected to said line, and means responsive to continuous current from said source when connected to said line for operating said ringer at intervals.

2. In a telephone system, a central office, a subscribers station, a line connecting said oflice and station, a ringing current source connectable to said line at said ofifice, a ringer connected to said line at said substation, and means operative on the continuous connection of said ringing source to said line for operating said ringer at intervals for periods of definite duration.

3. In a telephone system, a central ofiice, a subscribers station, a line connecting said central ofiice and station, a source of ringing current at said central ofiice connectable to said line, a ringer at said substation connected to said line, a three-element gas-filled discharge tube connected to said line at said substation, and means responsive to continuous current from said source when connected to said line for discharging said device at intervals and means responsive on each discharge of said device for operating said ringer.

4. In a telephone system, a central office. a subscribers station, a line connecting said central ofiice and station, a source of alternating current at said central office connectable to said line, an alternating current responsive ringer at said substation connected to said line, and means for operating said ringer at intervals by continuous when said source is alternating current from said source connected to said line.

5. In a signaling device, a source of current,

a signal, and means responsive said source for operating increasing in frequency.

6. In a signaling device, a a signal, and means responsive said source for operating to current from said signal at intervals source of current, to current from said signal at intervals at a rate increasing with time until a practically constant rate is reached.

'7. In a signaling device, asource of current, a

signal, and means responsive said source for operating increasing in frequency until the signal becomes to current from said signal at intervals operated practically continuously.

8. In a signaling device, a source of current,

a signal, ,and means said source for operating responsive to current from said signal at intervals constant in duration, but increasing in frequency.

9. In a signaling device, a source of current,-

a signal, and means including a discharge tube and responsive to current from said source for operating said signal by discharges from said tube at intervals increasing in frequency.

10. In a signaling device, a source of current,

a signal, and means including'discharge devices of the cold cathode type rent from said source and responsive to curfor operating said signal by discharges from said discharge devices at intervals increasing in frequency.

11. In a signaling device, a source of current, a signal, and means including an element having the characteristics of decreasing its resistance with time as current is applied to it and a discharge tube responsive to current from said source for operating said signal by discharges fromsaid tube at intervals increasing in frequency. y

12. In a signaling device a source of current, a signal, a discharge tube, a condenser, and means whereby the application of current from said source tosaid condenser causes the charging of said condenser to certain values at intervals increasing in frequency for operating said tube each time said condenser has accumulated said charge of a certain value and for operating said signal each time said tube is operated.

13. In a signaling device, a source of current, a signal, a discharge tube having two control electrodes and an anode element, a condenser in series with said control electrodes, a signal in series with said anode and said source of current, means including an element having a non-linear resistance characteristic for charging said condenser from said source of current, said tube, condenser and means for charging said condenser being so adjusted and connected that the condenser is charged and discharged through the tube to operate said signal at intervals increasing in frequency from the time the current is applied to said means until the frequency of said interval causes a practically continuous operating discharge over the anode of said tube for the continuous operation of said signal.

14. In a telephone system, a central office, a substation, a line connecting said central office and station, a source of current at said central oflice connectable to said line, a ringer at said substation connected to said line, and means responsive to current from said source when it is connected tosaid line for operating said ringer at intervals increasing in frequency.

' HAROLD A. BREDEHOFI'. 

